This study is to determine whether a chemically synthesized conjugated estrogen, that was developed in our laboratory, when provided to postmenopausal women, will increase their blood levels of estradiol. Twenty postmenopausal women will receive either 2.0 Mg of estrace or an equal molar amount of estradiol-3b-glucoside for two weeks. Blood samples will be obtained at appropriate times for the determination of circulating concentrations of estradiol and estrone.